The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
In direct injection engines, fuel is directly injected into cylinders. Spark ignition direct injection (SIDI) engines are one type of direct injection engines. SIDI engines may include a high pressure fuel injection system that sprays fuel directly into a specific region within a combustion chamber of each cylinder. A homogeneous or stratified charge may be created in the combustion chamber depending on engine operating conditions.
In SIDI engines, fuel may be injected into the combustion chamber in such a way that a small amount of fuel is placed in the vicinity of a spark plug for each cylinder. The air-fuel mixture in the vicinity of the spark plug is surrounded mostly by air, but is a fuel-rich mixture and can be ignited by the spark plug. Therefore, the SIDI engines can be operated in an ultra-lean-burn mode with an air fuel ratio as high as 65:1, as opposed to the stoichiometric ratio (14.7:1 for gasoline engines, for example) for normal operations where the fuel is homogeneously dispersed in the cylinder.
Fuel injectors inject fuel into cylinders of a SIDI engine according to timing and pulse widths that are determined by an electronic control module (ECM). A driver circuit energizes solenoid coils of the fuel injectors in response to the injection command pulse from the ECM. When the solenoid coils are energized, the injector valves of the fuel injectors are opened for a duration to allow the fuel to enter the combustion chambers of the cylinders. SIDI engines require accurate control of energizing current through the solenoid coils via the driver circuit to ensure a proper spray pattern and vaporization of the fuel.